1. Field of the Invention
The present invention relates to vapor compression systems, particularly, vapor compression systems having an evaporator defrost system.
2. Description of the Related Art
Conventional vapor compression systems typically include a refrigerant circuit through which a compressible refrigerant flows and which fluidly connects, in serial order, a compressor, a condenser, an expansion valve, and an evaporator. In operation, the condenser transfers thermal energy from the compressed refrigerant flowing therein to the ambient air surrounding the condenser, thereby warming the air and condensing the refrigerant. Meanwhile, the evaporator transfers thermal energy from the ambient air surrounding the evaporator to the compressed refrigerant flowing through the evaporator, thereby cooling the air and evaporating the compressed refrigerant. During this process, condensation may form on the evaporator surface. Under certain conditions, this condensation may freeze thus causing frost to accumulate on the evaporator surface. The accumulation of ice and frost on the evaporator surface may impair the ability of the evaporator to transfer thermal energy, thus resulting in reduced efficiency.
Accordingly, vapor compression systems may be equipped with a defrost system for melting the ice formed on the evaporator. Many such defrost systems provide a mechanism for temporarily blocking the flow of the compressed refrigerant to the evaporator, while directing the flow of a hot refrigerant to the evaporator to thaw or defrost the ice formed on the evaporator surface. Once thawed, the flow of hot refrigerant to the evaporator is ceased and the flow of compressed refrigerant to the evaporator is restored. Unfortunately, such defrost systems interrupt the operation of the compression system and the flow of refrigerant through the circuit, which may result in reduced efficiency and temperature fluctuations. Accordingly, a need remains for a vapor compression system having an effective and efficient defrost system for defrosting the evaporator surface.